"A little snack to start; the Underhive diet isn't half bad."
No matter what kind of "mutant overlord" ruled the sumps, it was no match for a Zerg swarm, let alone an elite evolution like Zehaka.
"Take him down, Zehaka."
Though the mutant possessed the mass of a super-heavy unit, it was still just a mindless aberration. Its thick skin, capable of shrugging off small-arms fire, could not stop Zehaka's mono-molecular claws.
Zehaka leaped nimbly onto the beast's head, plunging his talons deep into its skull. Despite the lethal strike, the creature thrashed frantically, its enormous body coiling with raw, desperate power. But Zehaka's grip was absolute.
"Don't even think about escaping."
Zehaka's tail lashed out, piercing the creature's cranium. With a brutal twist, he pulverized the brain matter. The beast went limp, its massive frame twitching with involuntary post-mortem tremors.
"That was barely an appetizer."
The Overmind didn't know whether to praise Zehaka's combat efficiency or pity the mutant's useless defenses. Armor-stacking was irrelevant; in a contest of pure biological lethality, Zehaka was the clear winner.
The Primal Zerg began to feed, and they ate voraciously. Many of the Ravasaurs were now the size of Roaches, and Zehaka had swelled significantly. Originally three meters tall, he now loomed at nearly six meters. His chitin had hardened into a matte-black shell, and his muscles rippled with a new, streamlined beauty.
"A good meal, but we're just getting started."
Even at this size, they were still within the realm of conventional weaponry.
"Continue devouring until this Hive can no longer contain you. Then, you shall dismantle their fortress."
"Yes, Master."
From that day on, peace fled the Underhive of Volkus. Even in a place where death is a constant, reports of "beast attacks" became an epidemic. Entire gangs vanished overnight, leaving behind nothing but bloodstains. However, with a planetary population exceeding ten billion, the disappearance of a few thousand gangers was barely a statistic.
Zehaka and his pack continued their gluttonous ascent until Zehaka's mass rivaled that of an Ultralisk. He no longer needed to hide. At this scale, even an Imperial Knight would struggle to bring him down.
This reached the limit Abathur had predicted for biomass-driven growth. Zehaka was now five times his original height and a hundred times his original weight.
"Can he get any larger, Abathur?"
"Negative," Abathur rasped. "As mass increases, skeletal integrity fails. Digestive, respiratory, and nervous systems require fundamental redesign. Proportional scaling is insufficient."
It was simple biology. Nerve signal transmission in a creature that large becomes a liability. Much like the ancient dinosaurs of Earth, which supposedly required secondary neural clusters to manage their hindquarters, a giant organism faces a "lag" in reaction time.
Furthermore, there was the oxygen problem. Modern insects are small because current oxygen levels cannot support giant respiratory systems.
"Lack of suitable genetic material," Abathur added. "Primal Zerg lacks specialized organs for extreme gigantism. Current environment provides only base biomass, not high-quality essence."
"I see. Eating gangers and sewer gators only goes so far. We need something... exotic."
"Individual gene sequences are inefficient," Abathur complained. "Primal Zerg keeps adaptations to itself. The Swarm shares. One Roach adapts, all Roaches adapt. Primal Zerg is selfish. Primitive. Falling behind."
Abathur clearly despised the "monopolistic" nature of Primal evolution. In the Swarm, evolution was a collective upgrade; in the Primals, it was a solitary hoard.
"You're right, Abathur, but this 'biomass injection' is a great way to boost combat power on short notice."
Zehaka finally made his move. He was now a true behemoth, and the Underhive could no longer mask his presence. His Ravasaurs had grown to the size of Dreadnoughts, and his Igniters resembled super-heavy tanks.
THUMP. THUMP. THUMP.
Zehaka led the way, his footsteps shaking the very foundations of the Hive. He unleashed a piercing roar that tore through the stagnant air, echoing for kilometers. The sound drifted upward, reaching the Mid-hive and even the Spire.
"What was that?"
"Sounds like a Great Beast... but it's coming from the sumps. I have a bad feeling about this."
Atlas, donning his Inquisitorial robes, stepped out of the courthouse. The streets of the Hive were eerily quiet, patrolled only by the Planetary Defense Force (PDF). Volkus was a fortress world, boasting two billion PDF soldiers and a million seasoned Astra Militarum troops. Between that and the Great Volkanon, neither Eldar nor Ork fleets dared to approach.
Atlas gazed at the distant mountain-cannon. It was a symbol of Imperial might, but also a target. He had always feared someone would try to sabotage it, even though it was as large as a mountain and shielded against orbital fire.
"I'm becoming neurotic," Atlas thought.
"Atlas! Atlas!"
His companion ran toward him, face pale.
"Something has emerged from the Underhive! A massive xenos organism is heading straight for the Volkanon! Arm yourself—we are heading to the front lines immediately!"
Atlas's unease had finally manifested. The hunt had moved to the surface.